3. put both in a dashboard and check whether the logic is working if you select D in first dashboard prompt and apply, you should get only A,B,C option in the second prompt.

4. Edit your main dashboard . put Dasgboard prompt1 in one section save.
5. Inside Edit dashboard only click on Dashboard Property (nest to preview button), you can see all the pages.
6. now select your page and click on 'select prompt...' (prompt symbol next to Rename) . Browse your second prompt and click ok,ok.